A. Technical Field
The present invention relates to a process for extracting a solid material packed in each reaction tube of a shell-and-tube reactor, for example, a packed material such as a catalyst used for a catalytic reaction of hydrocarbons.
B. Background Art
In the fields of petrochemical industry, many catalytic reactions, such as an oxidation reaction, an ammoxidation reaction, a decomposition reaction, a reduction reaction, and a reforming reaction of hydrocarbons, are carried out with a shell-and-tube reactor. The reactor used for these reactions is packed with a catalyst or inert filler suitable for each catalytic reaction.
The following techniques are concretely known.
JP-A-1484/2000 describes a production process for pyromellitic anhydride, which comprises the steps of: packing two or more catalysts including different components and vanadium as an essential component in a reaction tube; and carrying out a catalytic gas-phase oxidation of 1,2,4,5-tetraalkylbenzene.
JP-A-323950/1997 describes a production process for methacrolein, which comprises the steps of: packing a reaction tube with a catalyst including molybdenum, bismuth, and iron as essential components of which activities are controlled by changing a mixing ratio of an inert raschig ring; and carrying out a catalytic gas-phase oxidation of at least one kind selected from isobutylene and/or t-butyl alcohol.
JP-B-57906/1991 describes a production process for maleic anhydride, which comprises the steps of: packing a reaction tube with a catalyst including phosphorus and vanadium as essential components of which activities are controlled by changing a mixing ratio of an inert alumina pellet; and carrying out a catalytic gas-phase oxidation of n-butane.
JP-A-130722/1999 describes a production process for acrylic acid, which comprises the steps of: arranging a packed inert substance layer between a proceeding packed catalyst layer and a latter packed catalyst layer wherein the proceeding packed catalyst layer includes molybdenum, bismuth, and iron as essential components, and the latter packed catalyst layer includes molybdenum and vanadium as essential components; and carrying out a two-step catalytic gas-phase oxidation of propylene with one shell-and-tube heat-exchanging reactor.
When the catalyst as used for these catalytic reactions is used for a definite period, its activity or mechanical strength is generally lowered by such as poisoning, caulking or sintering. Therefore, the catalyst is extracted from the reactor and exchanged to a new catalyst each time.
When the catalyst is exchanged, the following method is employed as a method for extracting a solid material such as these catalysts in the reactor: a method that involves entering a worker in a reactor, and dropping a solid material in a reaction tube while the worker spears up with such as a metal thin stick from a lower opening portion of the reaction tube.
In addition, U.S. Pat. No. 5,228,484 describes a technique that involves: inserting a nozzle into a reaction tube from its upper end; blowing high-pressure air from a tip of the nozzle; unfastening or fluidizing the catalyst as packed in the reaction tube by the high-pressure air; raising and sending the catalyst into a filling room arranged at the upper end of the reaction tube by the high-pressure air; and exhausting the catalyst by vacuum-exhausting the filling room.
In the conventional method for extracting the solid material by using the spearing stick, whenever being speared by the stick, the solid materials such as the catalyst or these cracked materials in the reaction tube are dropped, and the solid materials as dropped are scattered on a floor and cause plenty of powdery dust. Therefore, the working environment is extremely poor foil the worker.
In addition, these materials as dropped and the powdery dust are often poisonous substances for human body. Therefore, the worker as employed in the extracting work requires putting on protectors, such as a dust-inhibiting wear, a goggle, a dust-inhibiting mask, and gloves.
Furthermore, the catalyst as used for these catalytic reactions may often include noble metals in high concentration. Therefore, the waste catalyst as extracted may be treated to recover metals. However, in case of a reactor of which reaction tube is packed with two or more kinds of catalysts and an inert substance as described in JP-A-130722/1999, the conventional extracting method results in mixing these catalysts and inert substance as dropped from the reaction tube and taking plenty of labor for classifying and recovering the catalysts.
In an industrial operation, a shell-and-tube reactor ordinary has hundreds to tens of thousands of reaction tubes. Therefore, when these solid materials such as catalysts in the reactor are extracted by the conventional method, not only a worker employed in the extracting work greatly feels bodily and mental pain but also the environment is badly influenced.
In addition, in the method that involves using the high-pressure air, the filling room is arranged at the upper end of the reaction tube. Therefore, the problem of causing the powdery dust is reduced. However, the method requires having air-tightness between the filling room and the upper end of the reaction tube, wherein the catalyst enters the filling room together with the high-pressure air. The high-pressure air nozzle as sent into the reaction tube penetrates and passes through the filling room. Therefore, there are also problems of air-tightness at this penetrated portion. As these airtight structures are complicated, the apparatus becomes a large-scale one, such that an apparatus having a mechanism of both supplying the high-pressure air and vacuum-exhausting is necessary, and the workability is not very good.
A. Objects of the Invention
Accordingly, an object of the present invention is to provide a process, which solves the problems of the prior arts, and involves safely and sanitarily extracting a solid material from a shell-and-tube reactor with good efficiency.
B. Disclosure of the Invention
The present invention is a process for extracting a solid material from a shell-and-tube reactor, which comprises the step of extracting the solid material that is packed in a reaction tube of the shell-and-tube reactor, with the process further comprising: the step (a) of inserting an aspirating tube from an end of the reaction tube wherein the aspirating tube is connected to an exhaust gas aspirator; and the step (b) of extracting the solid material from the reaction tube by aspirating the solid material in the reaction tube from a tip of the aspirating tube together with a stream of air.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.